青海省胃癌发病率及死亡率均居全国之首，藏族是青海省人口仅次于汉族的第二大民族，而藏族人群胃癌发病率明显高于汉族,且平均发病年龄较汉，回族为低，调查显示青藏高原地区世居藏族胃癌检出率高于25年以上的移居者，但HP感染率各民族间无差异。事实表明地理环境、饮食习惯、HP感染率均不能解释藏汉族胃癌发病率的差异。藏族有较严格不通婚习俗,保持了相对的基因独立，有研究表明藏族与汉族部分基因确实存在差异。因此，本课题采用microRNA芯片杂交和荧光定量PCR技术，系统检测青海世居藏族和汉族人群中胃癌组织、正常胃粘膜和循环血液中microRNA的表达量，结合统计学分析，阐明世居藏族与汉族胃癌组织及循环中microRNA的表达是否存在民族差异，明晰胃癌组织与外分泌到血浆中microRNA的表达是否一致，从分子水平探讨高原藏族胃癌高发的机制并且筛选出藏族胃癌特异性循环microRNA作为藏族胃癌早期筛检的分子标志物。

There is the highest Incidence rates and mortality of gastric cancer in Qinghai Province. Tibetan population is the second only to the Han in Qinghai province. But the incidence rates of gastric cancer of Tibetan was significantly higher than Han , and the average age of the gastric cancer occurrence is younger compared to the others. The study showed that detection rate of gastric cancer in the native Tibetan is higher than the settlers who moved here more than 25 years. Infection rates of H pylori had no difference among different ethnic groups. These results indicate that the geographical environment, diet habit, the infection rates of H pylori cannot be the reason of different incidence rates of gastric cancer between Tibetan and Han. Tibetan has strict customs of intermarriage, shows relatively independent genes, studies have shown that some genes expression are differences between Tibetan and Han. Therefore, in this study the expression of microRNA in native Tibetan and the Han gastric cancer tissues, normal gastric mucosa and plasma of cancer patients and healthy will be detected by microRNA hybridization and real time-PCR. Combined with statistical analysis , we can find if there are any different expression of microRNA in gastric cancer between Tibetan and Han which has been reported; if there are any differences of microRNA in the gastric tissue and plasma; find out the pathogenesis of higher incidence rate and specific circulating microRNA will be selected as biomarkers of the Tibetan gastric cancer.